possible valve issue

1 reply to this topic
  • joeyz17

Posted July 08, 2013 - 09:35 AM


I looked and couldn't find a similar thread for this issue but may have overlooked it.
I have a 2008 yz450f bought new in 2010.several hours on machine and sporatically acts like it has no compression.
mostly when hot.fires right up and runs smooth,so I check valves and only the center intake valve was off.pulled a180 shim out
and it took a 164 to get it perfect in spec. yet still only sometimes I go to crank ussualy warm after some riding it kicks over a few times
like it has absolutely no compression. I am suspecting a bucket sticking in the head and wondering before I go that far for nothing if anyone
has run into this...thanks

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted July 08, 2013 - 03:28 PM


It is likely that your temporary compression loss is the result of either worn rings (and/or a piston) or carbon deposits on the valve stem that are preventing the valve from fully seating by jamming the stem in the guide.

It's also unquestionable that the center intake in your engine needs immediate replacement before it drops the valve head on your piston one day.

Related Content


2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  57 replies

Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies

Is the 2016 GYTR Yamaha YZ450F too fast? by Fryboy

Dirt Bike   Special Interest Forums   Pro Racing
  • * - - - -
  • Hot  241 replies

Need help by Goforaride

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  68 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.